This invention relates to a liquid crystal display apparatus and, particularly, to a liquid crystal color display apparatus suitable for use as a pilot's or driver's instrument panel installed on the aircraft, automobile, or the like for displaying vehicle operational data in variable color.
There has been known a liquid crystal color display panel having an array of color filters provided on the transparent electrodes in the liquid crystal panel so that variable-color display is achieved by selective combinations of active electrodes, as disclosed in Japanese Patent Unexamined Publication No. 59-90818. In the arrangement of such a liquid crystal display panel made up of display pattern segments each having transparent electrodes covered by color filters and those without filters, different brightness is created among portions with and without color filters, and impaired legibility and appearance of display resulting from this structure has been a major problem of the liquid crystal color display panel. FIGS. 3 and 4 show the conventional liquid crystal color display panel applied to the automobile instrument panel 30, which includes a speedmeter section operative in variable color in the center and a fuel gauge section and thermometer section operative in fixed color on the left and right. The transparent electrodes in the variable-color display section are overlaid with color filters, and a different brightness is created in this section from that of the fixed color display sections due to a voltage drop across the filter film.
Another drawback of the conventional liquid crystal color display panel, in which color filters are provided only over transparent electrodes of each display pattern segment, is that the color filters are visible unseemly on the background even if the segment is not activated, and this also impairs the legibility and appearance of display. For example, the speedmeter section of FIG. 3 includes the unit digit made up of seven segments a, b, c, d, e, f and g, and when a character "7" is displayed, only segments a, b and c are activated. In this case, the inactive segments d, e, f and g are desirably invisible completely, but actually the presence of color filters makes these unlighted segments visible improrperly on the background.
There has been known a liquid crystal color display panel in a dot-matrix structure, as disclosed in Japanese Patent Unexamined Publication No. 59-10988. This apparatus includes thin film driving transistors formed on a liquid crystal substrate with color filters of red, green and blue formed over the entire panel surface. However, this type of liquid crystal color display panel is complex in its fabricating process, needs a sophisticated manufacturing facility comparable with that for semiconductor devices, and therefore is expensive in cost.